RU2260911C2 - Device for monitoring and controlling use of return-line resources of code-division multiple access satellite communication system - Google Patents

Abstract

FIELD: radio engineering.

SUBSTANCE: proposed device designed to monitor and control use of return-line resources of code-division multiple access satellite communication system when servicing subscribers imposing different individual requirements to quality of session servicing in compliance with priorities, as is the case with real departmental satellite communication networks and those under design has receiving and transmitting antennas, group-signal receiver and transmitter, groups of modulators and demodulators, groups of microprocessors, signal adder, energy calculation unit, logic speed control circuit, and power control unit; device provides for selective interrelated control of message transfer speed and power radiated by transmitters of subscriber stations.

EFFECT: enhanced use of return-line resources.

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Description

The invention relates to radio engineering and is intended for use in complexes of automated control of satellite communications systems with code access, providing priority customer service.

The term multiple access refers to the sharing of fixed resources of a communication system by multiple users. In code division multiple access (CDMA) systems using direct code sequence modulation for spreading, a set of orthogonal or near-orthogonal spreading codes is defined (each of them uses the entire channel bandwidth) and one or more specific codes [1]. Satellite communication networks in which CDMA is used consist of a combination of subscriber earth stations (AS), one or more central earth stations (CA), and at least one relay satellite (SR). The CA performs the whole range of tasks to provide a system resource at the request of subscribers, switch channels, control the quality of session services and, along with the radio channel equipment, includes a subsystem for automated control of a satellite communications network. In the satellite communications network, AS-SR-TsS lines, called straight lines, and TsS-SR-AS, reverse lines of communication, are organized. The purpose of the satellite communications network is to service the maximum number of subscribers with the required quality, providing voice, data, and facsimile communication services on demand with existing restrictions on the power of the emitted radio signal, frequency bandwidth, etc.

In CDMA, many subscribers share the resources of the communication network, while creating mutual interference with each other in the process of detecting their signals on the CA. With an increase in the number of subscribers served, the level of mutual interference increases, reducing the signal-to-interference ratio in the return line to a value below the permissible level, which ultimately leads to a decrease in the quality of session service.

One of the main indicators determining the quality of service is intelligibility in the transmission of voice messages and the delivery time of data and fax messages of a certain volume. Considering the technical aspects and construction features of any communication network to be known, these parameters depend on the information transmission speed of the message through the communication line, which is accessible to each subscriber, which in turn directly depends on the signal-to-noise ratio both in the forward and reverse links. This ratio, with the known processing method, uniquely determines the reliability of communication, an indicator of which in digital communication systems is measured in line bit (BER) or packet (FER) error coefficients. The level of mutual interference generated in the return lines determines the number of subscribers served by the system with the required quality, therefore, to maximize the number of subscribers to the satellite communications network, it is necessary to reduce the level of mutual interference in the return line.

Given the stringent energy restrictions associated with mutual interference in the satellite return link, and the need to service the maximum number of subscribers with the required quality, the problem arises of effectively managing the resources available to the network. Moreover, by the network resource, as applied to the return line, the authors mean the total radiation power of the speakers and possible high-speed transmission modes that determine the quality of session service.

A device for managing the resource of a communication network with code access is described in US patent No. 5056109 on "Method and device for transmitting power control in a CDMA cellular telephone system" [2]. This device controls the transmission power of subscriber stations in such a way that there is a decrease in the level of mutual interference at the input of the CA, providing the opportunity to increase the number of subscribers served. Moreover, regardless of the location of the subscribers, the signals received by the CA receiver have the same level. The closer the signal power level from subscriber stations at the input of the central station receiver to the minimum minimum for all return lines corresponding to the required quality of service, the lower the level of mutual interference in the network and, therefore, the higher the degree of utilization of communication system resources. Based on the description, the most effective option for such a device is to service subscribers with the same quality of service requirements. In the case of dissimilar requirements to the quality of service, it is possible that subscriber stations with requirements below the average in the network will emit a signal of greater power than necessary, which, on the one hand, reduces the degree of use of network resources, and on the other, creates an additional level of mutual interference at the entrance of the CA. The disadvantage of this control device is its low sensitivity to the individual nature of the requirements for the quality of session services with priority customer service, which is taken into account in most existing, so promising departmental and corporate satellite communication networks.

The closest set of essential features to the claimed device is the device described in US patent No. 96/06149 on "Method and device for setting the data transfer speed in a multi-user system" [3], which ensures the highest quality of user service on average in the entire multi-user communication system by controlling the data rate. The invention consists in measuring the degree of use of communication network resources for the forward and reverse communication lines, comparing it with a predetermined threshold value and changing the data rate or the number of subscribers served in accordance with the result of this comparison. The transmission speed is regulated using the vocoder described in US patent No. 08/004484 for “Variable speed vocoder” [4], depending on the intensity of the conversation and forced by commands from the CA. The advantage of this device is the ability to individually control the transmission rate for individual network subscribers, which is described as an embodiment of the application and allows for the possibility of taking into account individual requirements for the quality of session services. However, the claimed technical result is achieved under the assumption of equalization of the signal power of subscriber stations at the input of the CA, as described above, and does not take into account the possibility of additional adjustment of the radiation power of the signal in accordance with individual requirements for the quality of session service for each subscriber or group of subscribers of a certain priority. This fact is the main disadvantage of the prototype.

The technical result of the present invention is to increase the degree of utilization of the resources of the return link of a satellite communication network with multi-station code access for servicing subscribers with various individual requirements for the quality of session services in accordance with their priorities, by selectively interdependent control of the message rate and the radiated power of the transmitters of subscriber stations.

The specified technical result in the implementation of the invention is achieved by the fact that in a known device for monitoring and controlling the use of reverse link resources to a central host [3], comprising a receiving and transmitting antenna, a group signal transmitter, a group of modulators and demodulators, a group of microprocessors by the number of modulators, a signal adder , a group signal receiver, the output of which is connected in parallel to the inputs of the demodulators and the input of the energy level calculation unit, the output of which is connected to the input of the logic circuit Board speed, the output of which is connected to the second control inputs of the microprocessor, information outputs of which are connected to respective modulators and the control outputs are connected to a network controller (not shown in the diagram), is additionally introduced the power control unit. The group of inputs of the power control unit is connected to the control outputs of the microprocessors, and the first group of control outputs is connected to the first control inputs of the microprocessors. The second group of control outputs of the power control unit is connected to the inputs of the speed control logic. The power control unit consists of a priority allocation unit, a memory unit, a calculation unit, and a command generation unit. The inputs of the priority allocation block is the group of microprocessor control outputs, the outputs of the priority allocation block are connected to the group of inputs of the memory block. The group of outputs of the memory block is the first group of inputs of the computing unit, the second group of inputs of which is connected to the outputs of the network controller. The group of outputs of the computing unit is a group of inputs of the unit for generating commands, the first group of outputs of which is connected to the first control inputs of microprocessors, and the second group of outputs is connected to the inputs of the logic circuit for controlling the transmission rate.

The use of the power control unit return line as a part of the device for monitoring and managing the use of resources of the reverse line expands the device's functionality, allowing individual control not only of the message transmission rate, but also of the radiated power of the subscriber station transmitters within acceptable limits. This allows you to increase the number of simultaneously served subscribers by reducing the level of mutual interference at the input of the CA receiver.

Materials explaining the invention include:

figure 1 is a generalized diagram of a satellite communications system, explaining the composition and the relationship of its main elements;

figure 2 - diagram of a fragment of a satellite communications system, illustrating the influence of external conditions on the reception and transmission of data by the central and subscriber stations;

figure 3 - figure A is the dependence of the power levels of the AC signals at the input of the receiver of the CS R _VHC in all active channels N,

figure B - distribution of signal-to-noise ratios h ² active reverse channels N,

Figure B - distribution of data transfer rates for reverse channels N, illustrating the case of selective control of the data transfer rate and the same signal power levels at the input of the central station;

4 is a structural diagram of a monitoring and control device located at a central station for controlling the use of resources of a return link of a satellite communication system;

5 is a structural diagram of a control unit of the radiation power of the transmitters of the subscriber stations used in the device for monitoring and controlling the use of reverse link resources;

6 - picture A - dependence of the level AC power signal at the input of the receiver R CA _{CA Rin} in all active channels N,

Figure B - distribution of signal-to-noise ratios h ² active reverse channels N, illustrating the case of selective joint control of the data rate and radiated power of the transmitters of subscriber stations.

Figure 1 presents a diagram of a satellite communications system that implements code multiple access, which is described in US patent No. 4901307 "System and method of multiple access with a spread spectrum, using satellite or terrestrial repeaters (CDMA)" [5]. The main elements are the central station (DS) 1, the subscriber station (AS) 2 and the satellite repeater (SR) 3. In turn, the DS 3, interacting with the public telephone network, consists of an RF module 8, a group of modulators 8, a group of demodulators 10, a message processing processor 11, a network controller 12, a vocoder and a data processor 13, a receiving antenna 14 and a transmitting antenna 15. The main elements of the subscriber stations 2 are an RF module 8, a modem 16, a controller and a message processing processor 17, a vocoder and a data processor 13, and t also a transceiver antenna 18. The main elements of CP 3 are the direct transponder 19, the reverse transponder 20, the transceiver antennas 21 and 22. The direct communication line described above is represented by two sections: a straight line up 4 from the DS to the CP and a straight line down 5 from the CP to the speaker. The return line consists of sections connecting the speakers and the CP, - the return line up 6, the CP and the CA - the return line down 7 and includes a set of return channels provided at the request of the subscriber for the duration of the communication session.

In actual departmental satellite communication systems, there are differences in the procedure for servicing individual groups of subscribers. This situation is due to the fact that subscribers are representatives of different management levels, starting from the highest level, to which the division management belongs, and ending with the lowest, to which ordinary employees belong. At the same time, each control level is assigned its own priority (from 1 for the highest to n for the lowest), the number of priorities is determined by the number of levels.

In this system, the maximum number of subscribers served with the required quality is a function of the level of mutual interference. In satellite communication systems that use time or frequency multiple access, there is a “hard” limit on the number of subscribers served due to the finite number of time and frequency channels. When using code multiple access using the ALOHA protocol, there is a “soft” limit on the number of subscribers served. For this type of system, an increase in the number of subscribers served above this limit causes a decrease in the quality of service for all subscribers of the system, and the signal transmitted by each of the subscribers looks like interference or noise for other subscribers of the system. If the limit of the number of subscribers served by the system is exceeded, the level of mutual interference becomes quite high and exceeds the permissible value of BER or FER [3]. This is the main reason that makes it necessary to control the transmission rate in the reverse link.

Figure 2 illustrates other reasons leading to the need to control the transmission rate in the return line to reduce the level of mutual interference and increase the number of served subscribers. The first reason is the attenuation of the signal and its multipath propagation, caused by the presence of various kinds of obstacles 24 on the path of signal propagation from the speaker to the central speaker. The second reason is the additional attenuation caused by atmospheric phenomena in the form of precipitation 23. These phenomena are dynamic in nature, individual for each subscriber, due to their different location in space. Figure 2 shows various types of speakers 2, so speakers No. 1 and No. 2 are implemented as a personal satellite terminal designed for voice transmission, while speakers No. 3 are implemented as VSAT, which can be used for data transfer. This is an additional confirmation of the individual nature of the requirements for the quality of session services made by each subscriber.

In accordance with US patent No. 96/06149 on “Method and device for setting the data transfer rate in a multi-user system,” the operation of such a system and control of the data transfer rate is assumed when equalizing the power levels of the AC signals at the input of the DS receiver R _{I DS} in all active channels N, shown in Figure A of Figure 3 [3]. In Fig. B of Fig. 3, in the form of a bar chart, a variant of the distribution of signal-to-noise ratios h ² in active reverse channels is presented when the power levels of the AC signals are distributed at the input of the central circuit shown in Fig. A of Fig. 3. The broken curve shows the distribution of the required signal-to-noise ratio h _{2 TP for} each of the active N channels, taking into account the distribution of P _{ВХ ЦС} (Fig. A, Fig. 3) and various priorities of subscribers due to individual requirements to the quality of service. From Fig. B, figure 3 shows that in individual channels provided to subscribers with low priority, there is a significant excess of h ² over. h ² _TP . In Fig. B, Fig. 3 shows a variant of the distribution of data rates for reverse channels N for the above case. The differences in the values of the speeds R ₁ and R ₂ , as well as the corresponding h ² and h ² _{TP, are} due to the different type of transmitted messages. So, R ₁ corresponds to voice transmission, and R ₂ corresponds to data transmission. This circumstance allows the possibility of creating a higher level of mutual interference in individual channels with less stringent requirements for quality of service and, accordingly, a lower level of mutual interference in channels with more stringent requirements for quality of service. The implementation of the process of optimal redistribution of the radiated power of the AC in the return channels together with the data transfer rate in accordance with the nature of the individual requirements for the quality of session service and the number of active subscribers is achieved using the device for monitoring and controlling the use of resources of the return line of the satellite communication system shown in Fig. 4. This device consists of a receiving 14 and a transmitting antenna 15, a group signal transmitter 29, a group of modulators 9 and demodulators 10, a group of microprocessors 30 by the number of modulators 9, a signal adder 31, a group signal receiver 25, an energy level calculation unit 26, a speed control logic 27, power control unit 28. The output of the group signal receiver 25 is connected in parallel to the inputs of the demodulators 10 and the input of the energy level calculation unit 26, the output of which is connected to the input of the speed control logic view 27, the output of which is connected in parallel to the second control inputs of the microprocessors 30, the information outputs of which are connected to the corresponding modulators 9, and the control outputs are connected to the network controller 12 (not shown in the diagram). The group of inputs of the power control unit 28 is connected to the control outputs of the microprocessors 30, and the first group of control outputs is connected to the first control inputs of the microprocessors 30. The second group of control outputs of the power control unit 28 is connected to the inputs of the speed control logic 27. The power control unit 28 shown in 5, consists of a priority allocation block 32, a memory block 33, a calculation block 34 and a command generation block 35. The inputs of the priority allocation block 32 are a group of control their outputs are microprocessors 30, the outputs of the priority allocation unit 32 are connected to the group of inputs of the memory unit 33. The group of outputs of the memory unit 33 is the first group of inputs of the computing unit 34, the second group of inputs of which are connected to the outputs of the network controller 12. The group of outputs of the computing unit 34 is a group of inputs a command generation unit 35, the first group of outputs of which is connected to the inputs of microprocessors 30, and the second group of outputs is connected by inputs of a logic circuit for controlling the transmission rate 27.

A device for monitoring and managing the use of resources of the return line of a satellite communication system with code multiple access works as follows. Information signals and control signals transmitted by subscribers of the satellite communication system are received in the return line using the receiving antenna 14 and are fed to the input of the group signal receiver 25, where they are filtered and pre-amplified. From the output of the receiver 25, the signals are fed to the input of the energy level calculation unit 26 and the inputs of the corresponding demodulators 10. The calculated energy value from the energy level calculation unit 26 is transmitted to the speed control logic 27, which compares the energy of the received signal with a set of thresholds. According to the comparison result, the speed control logic 27 transmits a speed control signal to the first control inputs of the microprocessors 30 if the signal energy exceeds the value of the upper threshold or below the lower threshold.

Demodulators 10 convert the received information signals and control signals in each of the return channels into a data stream suitable for further processing and transmission to the first information inputs of microprocessors 30. From the control outputs of microprocessors 30, control signals are transmitted to the input of the network controller 12 and the inputs of the power control unit , and the information signal, if necessary, is transmitted to subscribers of the public telephone network (PSTN). The group of inputs of the power control unit is the group of inputs of the priority allocation unit 32, where the priority value of each subscriber is extracted from the control signal received at the access stage. From the output of the priority allocation unit 32, each allocated value is written to the memory unit 33, where for each return channel, the acceptable value of the bit (BER) or packet (FER) error coefficient is selected in accordance with the selected priority. From the output of the memory unit 33, the permissible BER or FER values go to the first group of inputs of the computing unit 34, the corresponding calculated BER or FER values from the output of the network controller 12 are received to the second group of inputs during testing of the return channel and information exchange. In the calculation unit 34, the deviation of the calculated BER or FER values from the corresponding allowable values for each of the return channels is determined. The calculation result goes to the command generation block, where two groups of teams are formed, the first group - commands to increase or decrease the power emitted by the transmitters of the subscriber stations 3, in accordance with the calculated deviations BER or FER goes to the second control inputs of the microprocessors 30. The second group of commands commands to increase or decrease the transmission rate in each of the return channels is supplied to the inputs of the logic control circuit of the speed and is additional to those commands that formed by the speed control logic described above. The microprocessors 30 combine the information signal with commands to increase or decrease the power radiated by the transmitters of the subscriber stations 3, and increase or decrease the transmission speed that are received at the first and second control inputs. From the information outputs of the microprocessors 30, the combined signal is fed to the corresponding modulator 9, which modulates the signal. From the output of modulators 9, the signal is fed to the adder 31 for combining and then converted to a form suitable for transmission in a straight line in the transmitter 29, and is emitted by the transmitting antenna 15. Figure A shows the dependence of the power levels of the AC signals at the input of the receiver R _{VX DS} in all active channels N for the case of selective joint control of the data rate and radiated power of the transmitters of the subscriber stations, and the power level P _{I DS is} not the same for all active channels N. In Figure B, Fig.6 In the form of a bar graph, a variant of the distribution of signal-to-noise ratios h ² in active reverse channels is presented when the power levels of the AC signals are distributed at the input of the CA, shown in Fig. And Fig.6. The broken curve shows the distribution of the required signal-to-noise ratio h ² _TP in each of the active N channels, taking into account the distribution of P _{ВХ ЦС} (Fig. A, Fig. 6) and various priorities of subscribers due to individual requirements to the quality of service. From figures A, B, shown in Fig.6, it can be seen that for all active channels the excess of h ² over h ² _TP exists or is significantly reduced, which leads to an increase in the degree of use of reverse link resources and, accordingly, expansion of the subscriber capacity of the satellite communication system with a code multiple access.

Thus, the analysis of the principle of operation of the inventive device for monitoring and managing the use of resources of the return line of a satellite communication system with code multiple access indicates the obviousness of the fact that, along with the saved management capabilities of the use of resources of the return line, the device is able to function efficiently by monitoring and controlling the use of resources during maintenance subscribers with various individual requirements for the quality of session service in accordance with with their priorities, which takes place in real-life departmental and corporate satellite communication systems.

SOURCES OF INFORMATION

1. Varakin L.E. Communication systems with noise-like signals. - M .: Radio and communications, 1985 .-- 384 p.

2. US patent No. 5056109 on "Method and device for controlling the transmission power in a CDMA cellular telephone system."

3. US patent No. 96/06149 on "Method and device for setting the data transfer speed in a multi-user system."

4. US patent No. 08/004484 on "Variable speed vocoder".

5. US patent No. 4901307 on the "System and method of shared access with extended spectrum, using satellite or terrestrial repeaters (CDMA)."

Claims (2)

1. A device for monitoring and managing the use of resources of the return line of a satellite communication system with code multiple access, containing a group signal receiver, the input of which receives signals from the receiving antenna, and the output of which is parallelly connected to the inputs of the demodulators and the input of the energy level calculation unit, the output of which is connected with the input of the speed control logic circuit, the output of which is connected to the second control inputs of microprocessors, the information outputs of which are connected to the inputs of of the corresponding modulators, and the control outputs are connected to the network controller, with the output of the modulators, the signals are transmitted to the adder, then they are converted in the transmitter and emitted by the transmitting antenna, characterized in that the power control unit is additionally introduced, and the group of inputs of the power control unit is connected to the control outputs of the microprocessors, and the first group of control outputs is connected to the first control inputs of microprocessors, the second group of control outputs of the power control unit is connected on with the inputs of a power control logic circuit. 2. The device for monitoring and managing the use of resources according to claim 1, characterized in that the power control unit consists of a priority allocation unit, a memory unit, a calculation unit and a command generation unit, the inputs of the priority allocation unit being a group of control outputs of microprocessors, the outputs of the allocation unit priorities are connected to the group of inputs of the memory block, the group of outputs of the memory block is the first group of inputs of the computing block, the second group of inputs of which is connected to the outputs of the network controller, g the group of outputs of the computing unit is a group of inputs of the command generation unit, the first group of outputs of which is connected to the first control inputs of microprocessors, and the second group of outputs is connected to the inputs of the logic circuit for controlling the transmission rate.

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